A number of circuit and architecture techniques in millimeter-wave (MMW) CMOS design and research have been developed, but many issues still remain. For instance, transmit/receive switches and high-efficiency power amplifiers are among critical issues that must be addressed. A transmit/receive switch is usually a SPDT switch, which is typically realized with two SPST switches plus an impedance matching network.
There have been various designs of transmit/receive switches in CMOS for MMW applications. Y. A. Atesal et al. (“Low-loss 0.13-um CMOS 50-70 GHz SPDT and SP4T switches,” in IEEE RFIC Symp. Dig., June 2009, pp. 43-46) describes a 50-70 GHz SPDT switch, as shown in FIG. 1. The SPDT switch 100 uses two symmetric SPST switches 110 based on the π-network. The input matching network is realized with quarter-wave length impedance transformers 120, which may consume a larger die area. This may result in a larger die size, e.g. a die size of 0.39×0.32 mm2 in Y. A. Atesal et al.